A main problem with the prior art hydro-pneumatic pressure transformers resides in the sealing between the storage chamber and the control chamber, because the hydraulic pressures in the storage chamber and the pneumatic pressures in the control chamber continuously change in the course of a work cycle, and this is not necessarily synchronously. Thus, there is the danger, on the one hand, that oil from the storage chamber reaches the control chamber and leakage losses are created by this, which could impair the work capacity of the hydro-pneumatic pressure transformer. On the other hand there is the danger of air from the control chamber reaching the storage chamber, where it is absorbed by the oil with the disadvantage that it reaches the work chamber and tends there to create increased compressibility in the high-pressure phase of the pressure stroke, along with all the disadvantages for the work capability resulting therefrom.
For this reason, in a known hydro-pneumatic pressure transformer of the species (German Published, Non-Examined Patent Application DE-OS 28 10 894), two radial seals are provided toward the wall of the work cylinder as well as the jacket face of the plunger piston, which have the purpose of achieving an optimal separation of the air from the oil. In this case it is particularly problematic that the tendency of the air to move from the control chamber to the storage chamber is not at all evident in the low pressure phase, but in the high pressure phase, in the course of which small amounts of air are also "pumped so that they bypass" the radial seals in the form of wall laminates during the axial movement of the storage piston.